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Continuum generation

Continuum generation is the creation of a white laser beam of light containing all the colours of the rainbow.  This is in contrast to most normal lasers which are just one colour e.g. red or blue.  Continua sources contain all of colours that are in sun or room light but in a very narrow laser beam. 

The continuum is generated when a femtosecond laser beam, made up of very short pulses of light (less than 1 millionth of 1 millionth of a second long), is incident on certain materials, such as the Mesophotonics continuum generation chip.

Continuum generation and Mesophotonics

 Schematic of tapered continuum generation chip
The unique properties of Mesophotonics technology means it can be used for white light continuum generation.

The combination of Mesophotonics materials and waveguides has enabled a revolution in continuum generation, giving unrivalled combinations of high resistance to damage, low threshold, high stability and broad spectral output all from silicon based chips measuring only 10x10x1mm.

The continuum output shows an exceptional smooth output spectrum with no visible spectral noise.  The lack of noise is a result of designing the waveguides to operate far from the zero of group velocity dispersion, thus avoiding the competing non-linear processes that are present in the high noise continuum generated in optical fibres. Mesophotonics CGC chips are designed for the efficient generation of white light continuum from femtosecond pulses of at least 10nJ energy at around 800nm.

 Mesophotonics tapered waveguide continuum generation chip
In terms of threshold and damage, Mesophotonics continuum generating chips (CGCs) combine the best of bulk and fibre media.  Continua can be generated with pulse energies as low as 10nJ - far lower than threshold observed in bulk media and comparable to that observed in fibre.  Meanwhile, damage testing has shown the waveguides capable of withstanding femtosecond pulses, with energies of several picoJoules and several watts of blue light - far higher than fibres and close to bulk media such as sapphire.

Continuum applications

White light continuum light sources have numerous applications including optical coherence tomography, where the continuum light source is used to detect cell level abnormalities in skin and other soft tissue.

Continuum white light sources are also used in a range of scientific applications where materials’ characterisation can be improved according to how samples interact with such a broad range of colours.  Recently techniques have also been developed to generate the world’s most accurate clocks and time standards using continuum light sources.

For more information on Mesophotonics continuum generation chips please contact us.